I found a good carbon calculator at the Safe Climate site. I won’t be able to get our own totals until I’m back home with the utility bills, but it does give some of the key conversion ratios:
- heating oil – multiply gallons of oil by 11.81 to get kgs of CO2
- petrol – multiply gallons by 8.87
- air travel – multiply air miles by .29
By the way some sites quote in carbon rather than carbon dioxide, so it’s worth knowing that 1 unit of CO2 is equivalent to .2729 units of carbon.
To calculate a family’s total footprint, multiply domestic use (including all travel) by 2.5, to cover all the other societal uses, since typically domestic use is around 40%.
Solar panels: a 4 x 8 foot glazed panel can generate (at the low end which is what it would be for us) 1,500 kWh a year. So we’d need a few to make the impact we need, even if we could achieve this level with so many trees around (but good news of those trees coming up). If instead the panels are producing hot water, then the right array typically produces around 75% of hot water needs in summer and 10% in winter (low ends again). And the panels (which are thicker than PV) can come in varieties that contain anti-freeze or gas, so that they also work to some extent in winter.
Now the good news on trees. An acre of forest will soak up 200 tons of CO2 over 40 years. So at 5 tons a year our woodland cover (which we could conservively estimate at 3 acres) would absorb 15 tons a year. And we should easily be able to stay under this limit, even with a reasonable amount of air travel. On the other hand, should the fact that we could afford to buy this piece of woodland let us off the hook in this way?
Another Canadian site I’ve just found along the same lines is the OneTonne Challenge site.